Quick Review Flashcards - Click to flip and test your knowledge!
Question
What is the term for a force applied in a direction normal to a surface?
Answer
Thrust.
Question
How is the thrust exerted by a body placed on a surface related to its weight?
Answer
The thrust is equal to the weight of the body.
Question
Is thrust a scalar or a vector quantity?
Answer
Thrust is a vector quantity.
Question
What is the S.I. unit of thrust?
Answer
The Newton ($N$).
Question
What is the C.G.S. unit of thrust?
Answer
The dyne.
Question
How many dynes are equivalent to $1$ Newton?
Answer
$1\text{ N} = 10^5\text{ dyne}$.
Question
What is the gravitational unit of thrust in the M.K.S. system?
Answer
The kilogram-force (kgf).
Question
What is the conversion factor between $1\text{ kgf}$ and Newtons?
Answer
$1\text{ kgf} = 9.8\text{ N}$.
Question
What is the conversion factor between $1\text{ gf}$ and dynes?
Answer
$1\text{ gf} = 980\text{ dyne}$.
Question
Pressure is defined as the _____ per unit area of a surface.
Answer
Thrust.
Question
What is the mathematical formula for pressure ($P$) in terms of thrust ($F$) and area ($A$)?
Answer
$P = \frac{F}{A}$.
Question
Is pressure a scalar or a vector quantity?
Answer
Pressure is a scalar quantity.
Question
What is the S.I. unit of pressure?
Answer
The pascal (Pa).
Question
How is one pascal (Pa) defined in terms of Newtons and metres?
Answer
$1\text{ Pa} = 1\text{ N m}^{-2}$.
Question
What is the C.G.S. unit of pressure?
Answer
The $\text{dyne cm}^{-2}$.
Question
How many $\text{dyne cm}^{-2}$ are equivalent to $1\text{ N m}^{-2}$?
Answer
$1\text{ N m}^{-2} = 10\text{ dyne cm}^{-2}$.
Question
How many Newtons per square metre are equivalent to $1$ bar?
Answer
$1\text{ bar} = 10^5\text{ N m}^{-2}$.
Question
What is the value of one millibar in bars?
Answer
$1\text{ millibar} = 10^{-3}\text{ bar}$.
Question
What is the standard atmospheric pressure expressed in metres of mercury ($Hg$)?
Answer
$0.76\text{ m of Hg}$.
Question
What is the value of $1$ atmosphere (atm) in Pascals?
Answer
$1.013 \times 10^5\text{ Pa}$.
Question
The unit 'torr' is equal to how many millimetres of mercury?
Answer
$1\text{ torr} = 1\text{ mm of Hg}$.
Question
How many torr are equivalent to $1$ atmosphere (atm)?
Answer
$760\text{ torr}$.
Question
On which two factors does the pressure exerted on a surface depend?
Answer
The magnitude of thrust and the area on which it is applied.
Question
How does increasing the area of application affect the pressure for a given thrust?
Answer
The pressure decreases.
Question
How does increasing the thrust affect the pressure on a given area?
Answer
The pressure increases.
Question
Why are the ends of nails or pins made pointed?
Answer
To exert large pressure with less effort by reducing the area of contact.
Question
Why are wide wooden sleepers placed below railway tracks?
Answer
To reduce the pressure exerted by the iron rails on the ground by increasing the area.
Question
Why are foundation walls of buildings made wider than the upper walls?
Answer
To reduce the pressure exerted by the building on the ground.
Question
How does pressure in a solid differ from pressure in a fluid regarding the direction of exertion?
Answer
A solid exerts pressure only on the surface it is placed on, whereas a fluid exerts pressure in all directions.
Question
What is the formula for the pressure ($P$) exerted by a stationary liquid column of depth $h$ and density $\rho$?
Answer
$P = h \rho g$.
Question
In the formula $P = h \rho g$, what does $g$ represent?
Answer
Acceleration due to gravity.
Question
How is the total pressure in a liquid at depth $h$ calculated if atmospheric pressure ($P_0$) is considered?
Answer
Total pressure $= P_0 + h \rho g$.
Question
What are the three factors that directly affect pressure in a stationary liquid?
Answer
Depth ($h$), density of the liquid ($\rho$), and acceleration due to gravity ($g$).
Question
Does the pressure inside a liquid depend on the shape or size of its container?
Answer
No, it does not depend on the shape or size of the vessel.
Question
How does the pressure at a point in a stationary liquid vary with its depth from the free surface?
Answer
Pressure increases with the increase of depth.
Question
What is the relationship between liquid pressure and the horizontal plane in a stationary liquid?
Answer
Pressure is the same at all points on a horizontal plane.
Question
How does the density of a liquid affect the pressure at a given depth?
Answer
The pressure increases with the increase in density of the liquid.
Question
Why is the pressure at a certain depth in sea water more than at the same depth in river water?
Answer
Because sea water has a higher density than river water.
Question
Why is the wall of a dam made thicker at the base?
Answer
To withstand the higher pressure exerted by the water, which increases with depth.
Question
Why are water supply tanks placed at a high elevation?
Answer
To ensure greater pressure in the house taps, as pressure increases with the height (depth) of the water column.
Question
Why do deep-sea divers need special protective suits?
Answer
To withstand total external pressure that is much higher than their internal blood pressure.
Question
What happens to the size of a gas bubble as it rises from the bottom of a lake to the surface?
Answer
The bubble grows in size.
Question
Why does a gas bubble increase in volume as it rises in a liquid?
Answer
The pressure on the bubble decreases as its depth decreases, causing its volume to increase according to Boyle's law.
Question
State Pascal's Law regarding the transmission of pressure in liquids.
Answer
Pressure exerted anywhere in a confined liquid is transmitted equally and undiminished in all directions throughout the liquid.
Question
What is the fundamental principle behind the operation of hydraulic machines?
Answer
A small force applied on a smaller piston is transmitted to produce a large force on a bigger piston.
Question
In a hydraulic machine, if $A_1$ and $A_2$ are areas and $F_1$ and $F_2$ are forces, what is the governing ratio?
Answer
$\frac{F_2}{F_1} = \frac{A_2}{A_1}$.
Question
Why is a hydraulic machine referred to as a 'force multiplier'?
Answer
Because it allows a small input force to produce a much larger output force ($F_2 > F_1$).
Question
List two examples of hydraulic machines mentioned in the text.
Answer
The hydraulic press and the hydraulic jack (or hydraulic brakes).
Question
What is the use of a hydraulic press?
Answer
For pressing cotton bales, extracting juice from sugar cane, or squeezing oil from seeds.
Question
In a hydraulic brake system, what ensures that equal pressure is exerted on all wheels?
Answer
The transmission of pressure through the liquid in the pipe lines.
Question
What is the relationship between effort, load, and distance moved in an ideal hydraulic machine?
Answer
$\text{Effort} \times \text{distance moved by effort} = \text{load} \times \text{distance moved by load}$.
Question
How is the Mechanical Advantage (M.A.) of a hydraulic machine calculated?
Answer
$\text{M.A.} = \frac{\text{Load}}{\text{Effort}}$.
Question
In a hydraulic machine, is the distance moved by the effort greater or less than the distance moved by the load?
Answer
The distance moved by the effort is greater than the distance moved by the load.
Question
What happens to the pressure at point $B$ in a liquid if the pressure at point $A$ is increased by $10\text{ Pa}$ (assuming no depth change)?
Answer
The pressure at point $B$ also increases by $10\text{ Pa}$ due to Pascal's Law.
Question
Concept: 1 Atmosphere
Answer
Definition: The pressure exerted by a mercury column of height $0.76\text{ m}$ at sea level.
Question
What happens to the liquid pressure at a point if the diver moves horizontally?
Answer
The pressure remains unchanged.
Question
Which law explains why a liquid 'seeks its own level'?
Answer
The laws of liquid pressure.
Question
If a hydraulic press has pistons with areas $10\text{ cm}^2$ and $100\text{ cm}^2$, what is its force multiplication factor?
Answer
10.
Question
What property of liquids allows them to transmit pressure equally in all directions?
Answer
They are incompressible and have the tendency to flow.
Question
In hydraulic brakes, what component pulls the brake shoes back to their original position when pressure is released?
Answer
The spring.